Owoeye Accomodation 6 questions (2hr lecture) Flashcards
Automatic adjustment of the refractive state to maintain a focused retinal image. Occurs when responding to blur
Reflex Accommodation
This is the change in accommodation induced during fusional vergences. Leads to Convergence accommodation/convergence ratio (CA/C)
Vergence Accommodation
The refocusing that occurs due to the apparent (or perceived) nearness (proximity) of a target. Stimulated by targets located within 3 meters of an individual.
Proximal Accommodation
Lead of accommodation (SHE WILL MORE THAN LIKELY ASK US THIS)
Tonic Accomodation
What accommodation reduces with age?
Tonic Accommodation
What factors affect accommodation?
Blur Convergence Proximal issues Pharmacology Minus Lens Diseases
What are the 3 retinal image factors:
Contrast, Spatial frequency, retinal image motion
What are the 4 non retinal factors:
mood, voluntary effort, target luminance (brighter increases accommodation), training (vision therapy)
If i put a minus lens in front of anyone what will it do to the patients accommodation? What about a plus lens?
Minus lens makes the patient accommodate.
Plus lens the patient will not accommodate.
What are the 4 optical cues:
offer information about directionality (direction of image on retina, astigmatism is skewing accomodation), astigmatism, abberations
What are the 4 non-optical cues:
Size, Proximity (close up everything wants to kick in), apparent distance, depth cues
True/False: Contrast, spatial frequency and luminance factors have significant effects on accommodation.
False, have minimal accommodative error with these factors
True/ False: Retinal eccentricity, retinal-image velocity factors significantly effect accommodation.
True!
_______ occurs when the peripheral rays don’t coincide with the central and on axis rays. This makes the fuzz around the vision. “Rays that hit the outside of the frisbee aren’t clear as going through center of frisbee” “Kid goes under table to read”
Aberration
Variation/ small range in the image distance that is tolerable without a profound defocus.
Depth of Focus
True/False: Accommodation is sympathetic innervation.
False… parasympathetic
What drug has a very short half-life and should not be used to determine the cycloplegic refraction? (Lasts about 2.5 hrs.)
Tropicamide
These drugs are used for dialating the eyes and taking away accommodation.
Tropicamide, Cyclopentolate
Atropine, Homatropine, scopolamine- lots of side effects
_________ (drug) is effective with sufficient half-life, used frequently in peds.
Cyclopentolate
Why do you need peds to be dialated longer?
She said it takes away accommodation and she needs to correctly measure myopia because it is prevalent in young kids.
What is another word for dilation?
Mydriasis
Other drugs that affect accommodation: 8 things
Alcohol, Ganglion blockers, Phenothiazides and antidepressants, CNS stimulants, Marijuana, Carbonic Anhydrase inhibitors, antihistamines, morphine
Conditions that affect accommodation: a bunch of things…
Diabetes Traumatic Brain Injury (TBI) MS Down SYndrome Glaucoma Eye trauma Syphilis
What is a gradual age-related irreversible loss of accommodative amplitude? What age is it likely to happen?
Presbyopia, 2.5 D loss per year
40-45 years old
Complete loss 50-55 yrs old
What are the complaints from presbyopia?
Receded near point of accommodation
Blurred vision
Discomfort and asthenopia at near.
Contributing factors and biochemical changes that lead to the decrease of accommodation:
Lens thickness and size increases
ciliary muscle remains stable
zonules become less dense
What 3 factors do not change in presbyopia?
zonules still have their elasticity
Ciliary muscle still functions
motor neuronal pathway still functions
What Accommodation is treated with proper distance correction and VT (vision therapy) Plus lens wont help
Accommodative excess
What accommodation is treated with proper correction and vision therapy
Accommodative Infacility
What accommodation is treated with proper distance correction and plus lens.
Accommodative insuficiency
True/False: In accommodation there is convergence.
True
True/False: With no accommodation there is devergence
True
What are 2 ways to measure the AC/A ratio?
- Gradient determination
- Near-Far (or calculated) determination
Why is gradient determination better than near far determination? (SHE SAID SHE COULD ASK US THIS)
At the same distance proximal accommodation is controlled.
What is expected AC/A ratio?
3/1 to 5/1 or (3:1 to 5:1)
If near phoria is 2EP through subjective and then 7 EP through -1.00 D what is the AC/A ratio? and is it normal?
AC/A= (7-2)/1= 5/1
Yes it is wnl of expected of (3:1 to 5:1)
If near phoria is 2XP through subject and then 7 EP through -1.00D AC/A ratio is what? is the ratio normal?
AC/A= (7-(-2)/1= 9/1
Not normal
PAtient has PD=60 mm, 2XP at distance, 10XP at near (40cm)
Ac/A =PD(cm) + NFD (P’near- Pdistance)(m)
AC/A= 6+ 0.4 (-10–2)
= 2.8
